In an electrically controlled throttle apparatus, a driving device such as a motor controls an opening degree of a throttle valve in accordance with a position of an accelerator pedal stepped by a driver. The throttle apparatus made from a resin material is introduced to enhance the fuel economy, to reduce the weight and to reduce the cost. FIG. 19 shows the throttle apparatus made from the resin, which comprises a throttle body 101 forming an intake manifold, throttle vale 102 adjusting an air amount flowing through the throttle body 101, a throttle shaft 103 supporting the throttle valve 102, a power unit biasing the throttle valve 102 in opening direction, and a coil spring 105 biasing the throttle valve 102 in closing direction. An engine control device controls the power unit in order to adjust the opening degree of the throttle valve 102 according to a position of an accelerator pedal stepped by a driver.
The power unit comprises a driving motor 106 and a power transmitting device (reduction gears). The reduction gears include a pinion gear 110 which is connected with a motor shaft 109 of the driving motor 106, an intermediate gear 111 which engages with the pinion gear 110, and a valve gear 112 which engages with the intermediate gear 111. A throttle opening sensor is provided on an outer surface of the throttle body 101. The throttle opening sensor includes a permanent magnet 113 disposed inner surface of the valve gear 112, and a magnetic detector 114 which generates an electromotive force according to a magnetic field generated by the permanent magnet 113. The valve gear 112 is connected with one end of the throttle shaft 103. The magnetic detector 114 is a non-contact type detector and is disposed in a sensor holding portion 116 of a sensor cover 115 in such a manner that the magnetic detector 114 confronts to an inner surface of a yoke.
FIG. 20 shows a throttle apparatus of which throttle valve is driven by the driving motor. When the throttle valve is closed, an air tightness of the throttle valve depends on the clearance gap between an inner surface of the tubular throttle body 101 and an outer periphery of the throttle valve 102.
Conventionally, the throttle body 101 and the throttle valve 102 are independently manufactured in each different process. Subsequently, a manufactured throttle valve 102 is combined with a manufactured throttle body 101 in accordance with an inner peripheral dimension of the manufactured throttle body 101 in a downstream process. Alternatively, a manufactured throttle body 101 is combined with a manufactured throttle valve 102 in accordance with an outer circumferential dimension of the throttle valve 102 in a downstream process. Thus, a predetermined clearance is obtained between the bore inner periphery of the throttle body 101 and the outer circumferential periphery of a throttle valve 102. A throttle shaft 103 integrally rotates with the throttle valve 102. Both of the ends of the throttle shaft 103 are rotatably supported by cylindrical bearings 104 provided in the throttle body 101.
U.S. Pat. No. 5,304,336, which is a counterpart of JP-5-141540A, shows molding methods in which a manufacturing process of the throttle body and the throttle valve is reduced. In the molding methods, the throttle body 101 and the throttle valve 102 shown in FIG. 21 are integrally molded of a resinous material in the same molding dies. At first, the substantially tubular throttle body 101 is integrally molded of a resinous material. Subsequently, inner periphery (bore inner periphery) of the throttle body 101 is used as a part of a molding die molding the throttle valve 102, and the throttle valve 102 is molded. Thus, a shape of an outer circumferential periphery of the throttle valve 102 is adapted to a shape of the bore inner periphery of the throttle body 101 in the above molding methods.
The molded throttle body 101 is gradually cooled in the body cavity to be solidified. Subsequently, the movable die is slid forward in order to form a valve cavity, into which a resinous material is filled. The throttle valve 102 is molded of a resinous material in the throttle body 101.
However, in the above molding methods of the throttle valve 102, the throttle body 101 is molded of a resinous material while the molded throttle body 101 is restricted by dies in its radial direction and in its substantially circumferential direction. Thus, the throttle valve 102 is molded of a resinous material while the throttle body 101 and the throttle valve 102 are restricted by the dies. The throttle body 101 and the throttle valve 102 are taken out of the dies, and gradually cooled. In this cooling period, the unrestricted throttle body 101 and the throttle valve 102 are contracted. The throttle body 101 and the throttle valve 102 are deformed. Accordingly, it is difficult to maintain the clearance in a predetermined dimension between the inner periphery of the throttle body 101 and the outer circumferential periphery of the throttle valve 102.
A practical use of the throttle apparatus releases an internal stress, by which the apparatus is deformed. When the throttle apparatus is made from a crystal resin and is crystallized, the apparatus is deformed due to the crystallization thereof. Even the apparatus is annealed or aged, the throttle body 101 and the throttle valve 102 are deformed individually.
To solve the above problem, the inventors filed Japanese patent application No. 2003-285434 on Aug. 1, 2003. In this application, the throttle valve and throttle body is formed in a same die in such a manner that the throttle valve 102 is opened in a predetermined angle. A metal shaft is insert molded in a resin shaft of the throttle valve, and a first collar and a second collar are insert molded in the bore wall to support the both ends of the metal shaft. If a melted resin is introduced between the outer surface of the metal shaft and the inner surface of the collar during molding, the metal shaft hardly rotate in the collar. That is, the throttle valve may hardly rotate in the throttle body 101.
When the center axes of the first and the second collar deviate from each other, the throttle valve may hardly rotate in the throttle valve smoothly.